Long periods of wet weather lead to high risk of liver fluke

It seems the prolonged poor weather we have been having in the UK is finding more and more ways to have a detrimental effect on farming.

As forecast in 2012, this season's forecast indicates that there is a risk of very high levels of liver fluke disease in all of Scotland, Wales and western England. And, even though there are no figures available to produce a forecast for Northern Ireland, climate data also suggests that there is a high risk there too.

And, though the risk of fluke disease is thought to be high across the rest of the UK, the figures for East Anglia are at a level that is usually associated with a low risk of the disease.

But what is liver fluke disease? Well, it is a disease that is caused by a parasitic flatworm being present in the liver or sheep, but it can also be found in the liver of cattle.

The National Animal Disease Information Service (NADIS) has warned farmers that any localised areas that have remained wet for long periods of time over the summer and autumn may present a threat to livestock that are living on such land. They have also added that the fencing-off of such areas manages to provide some control of infection without increasing selection for flukicide resistance.

NADIS have also added that the first sign of a fluke issue on a farm could be seen in January, when poor scanning results are obtained. At this time of year, there is often a mixture of adult and immature fluke in the liver causing condition loss, dullness, anaemia, abdominal pain and sometimes death. This is termed sub-acute fascioliasis.

Deaths due to acute and sub-acute disease may continue in many regions into the winter. Mean daily maximum temperatures for November were just 10 °C in southern England, and lower across the rest of the UK, indicating that little fresh fluke infection will have been passing from snails onto the pasture.

However, the infectious stages (metacercariae) already on the pasture are highly resilient, so cases of acute fluke may therefore occur through January or even later, particularly in the high-risk regions. If there is severe penetrating frost, this will reduce their numbers and therefore reduce the risk of fresh infection of livestock.

Farms with a history of fluke should consider a winter (December/January) dose to remove adult and immature fluke. Sheep in high-risk areas may remain exposed to potentially risky pastures through the winter and consideration should be given to administering a repeat dose to these animals 4-6 weeks later.